This invention relates to axle suspension systems for wheeled vehicles. More particularly, it relates to certain unique axle-to-beam connections for suspensions of the rigid beam type.
Axle suspension systems of the rigid beam-type have been successfully used for many years, particularly by that segment of the heavy duty trucking industry known as over-the-road haulers, a portion of which is often referred to in slang terms as "18-wheelers". Because of the rather unique roll stability (i.e. "roll-stiff") characteristics of rigid beam-type suspensions, they find high utility on heavy, over-the-road trailers, usually having four-wheeled tandems, and their accompanying ten-wheeled (rear-tandem) tractors that pull them. While applicable to a wide variety of end uses to which rigid beam-type suspensions are put, the subject invention finds particularly high utility on these tractor-trailer rigs used in over-the-road environments.
The rigid beam of a rigid beam-type suspension may assume many forms and configurations. As used herein, then, the term "rigid beam" is used in its generic industrial sense to denote a beam which extends longitudinally of the vehicle to stabilize the suspension and transmit the forces of operation sent to it from the axle, to the frame member of the vehicle to which the beam is attached.
Beams of the "rigid" type are distinguished from beams which consist of a single leaf or a few stacked leaves of a leaf spring such that the beam is flexible to the point where it takes up the large majority or substantially all of the articulation forces experienced during vehicle operation, thereby eliminating the need for resilient connections at either the axle connection point or the frame member connection point (or both). Included within the term "rigid beam", however, is a leaf spring arrangement which is of a sufficiently thick or non-flexible configuration such that resilient mountings are required at one or both of the aforementioned points.
Rigid beams, while denoted "rigid", do, of course, flex during operation of the vehicle. This flexing is, simply stated, less than that of a conventional, flexible leaf spring type of beam; thus requiring resilient mountings at either or both of the two aforementioned points. Not only do such beams flex during operation, but they must be allowed to flex or, given reasonable sizes and thicknesses, they will break during vehicle operation. Indeed, early attempts to rigidify connections in the beams either at the frame connecting member (e.g. a hanger bracket) or at the axle connection (or at both) without providing sufficient resiliency at one or both of the connections proved futile in that frequent beam breakage was experienced.
One early solution to this problem was to provide a relatively small resilient pivot bushing at the hanger bracket connection and to wrap the axle in a resilient bushing. While somewhat successful, wear-out of the resilient bushing members was a frequent problem. In addition, the axle seat could not be welded or rigidly connected to the beam. Rather, it was held to the beam by U-bolts or a clamping mechanism, alone. Thus, if the U-bolts or clamp failed, there was nothing to hold the axle to the beam.
In an attempt to remedy such a situation, various resilient pin bushings and axle, or axle connection, wraps were developed. One such attempt was a two-pin bushing connection. An example of such a connection is described in U.S. Pat. No. 3,332,701. In this device, a pair of longitudinally spaced pins are used to connect the axle seat to the beam. This allows the beam to flex to a degree, while providing the ability to rigidly connect the axle to its axle seat. The pins, however, must be provided with resilient wrap-around bushings, and a bushed pivot connection at the hanger bracket is also provided. Resilient bushings are prone to wear out, as discussed previously. The 2 pins, furthermore, constitute the only real means for holding the axle in the beam. Pin failure meant axle or beam loss because there was no redundancy. U-bolts, while they could conceivably be used, could only be used with difficulty, since the 2 spaced pins were usually at a place that would interfere with U-bolt connections.
In a relatively recent development by the subject inventor, a significant improvement was made over the then existing prior art by the use of a two-piece axle seat which wrapped around the beam. The axle seat, axle, and beam were clamped together by U-bolts. Bushings were not required at the axle-to-beam connection and the moments were reduced by a pair of horizontal, longitudinally spaced plates connected to the bottom plate member of the upper part of the two-piece axle seat. When assembled, the two horizontal, longitudinally spaced plates laid flat against the upper plate of the beam, thereby spacing the axle seat above the upper plate of the beam except for the two spaced contacts it made with the two plates. The axle seat could not, however, be directly welded to the beam for a truly rigid connection because the construction still impeded flexing of the beam enough to discourage direct rigid welding. Rather, the beam, through a unique axle alignment technique described in U.S. Pat. No. 4,261,597, was welded to a horizontal extension plate extending from the U-bolt flange of the axle seat. The horizontal extension plate was found to be sufficiently flexible when connected to the beam at a spaced distance from the seat, so that, in combination with the pair of longitudinally spaced horizontal plates serving to space the axle seat from the upper surface of the beam and the axle seat beam being U-bolted only to the beam, the beam was sufficiently flexible to attain highly advantageous wear and safety characteristics. While quite acceptable, there still was not achieved a true and fully rigid axle-to-beam connection, such that the axle seat became a truly integral part of the beam. The welding that could be done at the extension plate served as a back up to potential U-bolt failure, but was not maximal in this regard, since the amount of welding was small. In addition, the techniques involved required complexities not readily adaptable for field servicing and repair. Furthermore, the lower piece of the axle seat was a wrap-around connection which reduced clearance.
While prior units, as above described, have proven to be and are considered safe and effective for their intended purpose, it is apparent from the above that there exists a need in the art for a new axle-to-beam connection in which the axle seat becomes a truly integral part of the beam without the need for resilient bushings or resiliently bushed pins in the connection, and wherein U-bolts, or clamps, if used, become a redundancy for safety, rather than the primary means of connecting the axle seat to the beam.
This invention fulfills this and other needs in the art more apparent to the skilled artisan once given the following disclosure, by providing for the first time, an axle-to-beam connection wherein the axle seat can be rigidly connected to both the axle and beam while allowing the beam to flex, thereby to provide an axle-to-beam connection that is truly rigid and integral with the axle and beam.
Generally speaking, this is accomplished by providing an axle suspension system of the rigid, longitudinal beam-type for a wheeled vehicle, wherein said longitudinal beam is provided with a first means for connecting the beam to a frame member of the vehicle and a second means for connecting an axle to the beam at a location spaced from said first means, the improvement comprising as said second means, a pair of longitudinally spaced members extending laterally across and being rigidly attached to said beam and an axle seat having a first and a second surface, said first surface forming a rigid connection with said pair of longitudinally spaced members without contacting the beam, and said second surface rigidly connecting the axle to said axle seat, thereby to provide a rigid axle-to-beam connection in which said axle seat does not come into direct contact with said beam.
In certain preferred embodiments the suspension is connected to the frame member of the vehicle by a resilient bushing connection as disclosed in the subject inventor's U.S. Pat. No. 4,166,640 (e.g. FIGS. 5-8 and accompanying discussion). When such a connection is used, the resulting suspension presents to the art an exceedingly strong, highly roll and brake torque resistant, and long-wearing suspension having a wide variety of end uses, but particularly useful as a heavy duty trailer suspension for long mileage, over-the-road freight hauling trailers.
In still further preferred embodiments, the pair of longitudinally spaced members extending laterally across the beam are in the form of two trapezoids that have a common large base, and the axle seat comprises a pair of laterally spaced, longitudinally extending plate members of substantially the same configuration. This allows for several advantageous features. Firstly, by locating the shorter base end of one of the trapezoids of the lateral plates against the inner wall of the beam, and providing the shorter base of a dimension slightly less than the outside width of the side walls of the beam, a continuous weld between the side walls and bottom or top wall of the beam (i.e. the wall opposite that associated with the axle) may be obtained, as can a continuous weld between the side walls of the beam and the lateral plates. The lateral plates, in this way, become an integral part of the beam; yet there is very little interference with the flexing of the beam.
Secondly, by providing both the longitudinal and lateral plates with the same "double-abutting" trapezoid configuration, an eared overlap can be provided at the maximum width of both plates, with a uniform cross-sectional configuration between them in the area (or zone) of overlap, regardless of whether the view is taken from the lateral, or longitudinal plate. This maximizes strength and material efficiency, allows for the contact to be outboard of the side walls of the beam, allows welding of the contact joints, avoids axle seat contact with the beam, particularly the top and bottom plates thereof that must flex in tension and compression, and allows for maximized flexing of the laterally extending plates because of the outboard nature of the contact point. Thirdly, by providing a cutout in the lateral plates flush with or below the axle-side surface of the side walls of the beam, the plate of the beam immediately adjacent the axle may be a continuous plate, which because it is spaced from the axle seat, is free to flex naturally, despite the fully integral nature of the axle-to-beam connection.
This invention will now be described with reference to certain embodiments thereof, as illustrated in the accompanying Figures, wherein: